[ggm]

there are elements of correlation/causation in this, so I think it's still "not clear" -But I too would think overall economic improvement reduces the "need" (for want of a better word) of pragmatic crime by poor people.

IoT like nest and other things may also make people wary of casual crime, its much more likely you're on film. I know there is a really good privacy concern around ubiquitous cameras but the other side of the coin is older, insecure and scared people who gain some comfort from knowing somebody can see whats going on around them. Ubiquitous digital cameras emerged across this timeframe.

Japan's crime culture is ideated by westerners as "about them, not us" -but this is about crime by Japanese on Japanese so it's outside that model. Certainly as a sometime frequent western visitor to Japan I have never felt the degree of situational risk I have felt in other economies, just being on the streets. It is a place where the most likely outcome of dropping your wallet is to have somebody help get it back to you. Most likely, not only.

Maybe theft from other Japanese really has declined, for it's own reasons? Maybe people no longer think its worthwhile? Which tends to the economic argument. Why steal that trivial bit of plastic and metal, if you can buy it in the 100 yen shop?